The present invention relates to a target made of a ferromagnetic material, a magnetron source, a magnetron sputtering system and to a process for producing a target made of a ferromagnetic material.
It is known that magnetron sputtering sources have a target as well as a magnet arrangement situated underneath. This magnet arrangement generates above the sputtering surface of the target a tunnel-shaped stray field which is normally looped in itself and which is decisive for the effect of the sputtering source as the magnetron sputtering source. During the magnetron sputtering of targets made of a ferromagnetic material, the latter act as a magnetic short circuit. Therefore, a sufficient tunnel-shaped stray field can be implemented only in the case of relatively thin target plates or else very strong magnets must be used. Nevertheless, the service life of the target and its yield of material remain low because, as soon as the formation of the erosion trough starts at the target, the stray field intensity in the trough area will increase which, in the sense of a regenerative system, results in an increasing contraction of the erosion trough with a correspondingly poorer yield of target material and a high rate loss by the sputtering deposit on the target.
U.S. Pat. Nos. 4,401,546 and 4,412,907 and DE-A-32 23 245 describe attempts to solve this problem by segmenting the target plate bonded onto a carrier plate to the carrier plate by way of slots. The division of the target plate into individual components requires extremely high manufacturing and cost expenditures. In addition, it must be ensured by the appropriate design of the intermediate spaces that the contamination of the sputtering process by the carrier plate material is minimized.
U.S. Pat. No. 4,299,678 suggests that the above-addressed problem can be counteracted in such a manner that grooves are machined into the target plate which do not extend therethrough, but instead the ferromagnetic target material is heated above Curie temperature.
In addition to the working-in of the surrounding groove pattern, in this case, the heating of the target, in particular, also requires extremely high expenditures. For example, heating to above 350.degree. C. is required for a nickel target.
Finally, EP-0 210 858 describes targets which have a blind hole pattern. They are used for non-magnetron high-frequency sputtering and consist, for example, of Mo, Cu, C or SiO.sub.2. Other metallic and dielectric materials can also be used. The blind holes are dimensioned such that one cylindrical cathode charge respectively burns therein, whereby a particularly high plasma density is to be achieved. An alternative approach is used in this case for high-frequency sputtering for the magnetron sputtering which is rare in the case of high-frequency applications.